1. Field of the Invention
The present invention relates to the removal and reinstallation of bottom entering agitator seals, and more particularly, but not by way of limitation, to an improved method of removing and reinstalling seal units wherein a movable selectively elevatable table is utilized.
2. Description of the Prior Art
Process vessels which include internal agitators are commonly used in refineries, chemical plants and other similar facilities. In a number of such vessels, the agitator is driven by a vertical shaft which extends through an opening in the bottom of the vessel. A seal unit is provided connected to the vessel which prevents reactants or other fluids within the vessel from leaking out of the vessel around the agitator drive shaft. The seal unit is connected to a coupling shaft, generally including one or more universal joints, which is in turn connected to a rotary drive means such as an electric motor operably connected to a right angle gear box.
The seal units and connector shafts of large agitator assemblies are heavy, and when it is necessary to repair or replace such seal units, the removal and reinstallation thereof has been very difficult. One procedure followed prior to the present invention for removing and reinstalling seal units in a vertically positioned bottom entering agitator assembly has been to remove the coupling shaft extending between the seal unit and the rotary drive means and then to lower and raise the seal unit, agitator shaft and agitator attached thereto in order to secure the agitator and agitator shaft within the vessel using a forklift truck with a platform attached to the forks. Because the weight of the seal unit, agitator shaft and agitator is carried off-center on the forklift truck, the load on the truck is unstable and often causes the seal unit to tip and bind which presents a serious safety hazard.
In an improved procedure described in U.S. Pat. No. 4,358,885, issued Nov. 16, 1982, a jack is substituted for the forklift truck in the lowering and raising operation. While the method using a jack is an improvement, the removal of a seal unit from the jack or placement of a seal unit on the jack is still difficult and dangerous to personnel as is the removal and reinstallation of the coupling shaft.
By the present invention, an improved method is provided which eliminates the safety hazards mentioned above and which brings about the more efficient removal and reinstallation of seal units thereby reducing equipment down time.